Fluid and system for preparing hydrogen sulfide sensitive tape



Dec. 16, 1958 Filed Aug. 15, 1956 v. SORG ET AL 2,864,725 FLUID ANDSYSTEM FOR PREPARING HYDROGEN SULFIDE SENSITIVE TAPE 2 Sheets-Sheet lDec. 16, 1958 v. SORG ETAL FLUID AND SYSTEM FOR PREPARING HYDROGENSULFIDE SENSITIVE TAPE 2 Sheets-Sheet 2 Filed Aug. 15. 1956 v/zer zr/mgyq ldz FLUID AND SYSTEM FOR PREPARING HY DRO- GEN SULFIDE SENSITIVETAPE,

Leonard V. Sorg and Elmer Bradley Olfutt, Kansas City, Mo., assignors toStandard Oil Company, Chicago, Ill., a corporation of IndianaApplication August 15, 1956, Serial No. 604,169

Claims. (Cl. 117-83) This invention relates to the continuous treatmentof strip material and, in particular, comprises improved apparatus forsensitizing one coated surface of tape or other strip material.

The manufacture of our sensitive film includes the steps of applying aliquid sensitive gelatin coating on a film support such as a continuoustransparent and fluidimpervious tape. Subsequently, the coated tape issensitized by impregnating the gelatin with a reactive solution.

In connection with a hydrogen sulfide analyzer-recorder described in ourco-pending patent application Ser. No. 375,032, now issued as U. S.2,800,397, we employ a sensitive-to-hydrogen-sulfide tape whichcomprises an acetate film base having a gelatin coating. Thiscorresponds to motion picture film from which the photosensitive silverhas been removed. By impregnation, we place a certain amount of leadacetate and sodium acetate into the gelatin coating.

An important object of the invention is to provide an improved apparatusfor continuously feeding tape or other strip material over a treatingsolution to effect a controlled impregnation of a gelatin coatingthereon. A further object of the invention is to provide an apparatusfor the rapid, accurate and uniform treatment of the gelatin coatingwithout injury or mutilation of the base strip material. A more specificobject of the invention is to provide an apparatus which prevents thesensitized or gelatin side of the tape from coming in contact with theparts of the apparatus along which it moves to permit the use ofrelatively small amounts of treating solution, to provide means formaintaining the surface of the solution at a constant level, and tomaintain the solution at the desired temperature.

Another object of the invention is to provide a system utilizing asensitizing station and a drying chamber with means for feeding thesupporting tape through the station and chamber in series so that thetape will be maintained in such a position that the sensitized gelatincoating is dried without contacting any portion of the apparatus. v

Still another object is to provide'a system which controls thetemperature and circulates air in the drying chamber whereby there is aprogressive drying of the coating to produce a non-tacky sensitizedstrip. Thes eand other objects of our invention will become apparent asthe description thereof proceeds.

Briefly, we attain the objects of our invention by providing means'forsuccessively impregnating and drying a gelatin coating on afluid-impermeable tape or base material which includes atemperature-controlled impregnat- 2,864,725 Patented Dec. 16, 195s.

Figure 1 is an elevation, partly in section, showing one form ofapparatus for impregnating a gelating coating on a continuous supportand for drying the impregnated coating;

Figure 2 is a side elevation, partly in section, of the apparatus shownin Figure 1;

Figure 2a is an enlarged fragmentary'section of the trough; I

Figure 3 is a detail taken along the lines 33 in Figure 1; I

Figure 4 is a detail taken along the lines 4-4 in Figure 1;

Figure 5 is a detail taken along the lines 5-5 in Figure 1;

Figure 6 is a detail taken along the lines 6-6 in Figure 3; and

Figure 7 is a detail taken along the lines 77 in Figure '2.

Similar reference numbers refer to corresponding parts in the severalviews of the drawings.

Referring to the drawings, the framework 10, comprising angle irons,supports 0.25 inch aluminum panel 11 upon which all of the components ofour apparatus are mounted. Four bolts or feet 12 extending through thelateral surfaces of the angle irons 10 permit adjusting the apparatus toa level position.

V the instrument.

ing station which is provided with means for accurately -I A compartment13 comprised of walls 13a and hinged cover 14 comprises the dryingchamber.

A motor 15, controlled by switch 16 and fused by 17, provides the drivefor moving the filmor tape through Gears 18 and 19 driven by motor 15drive sprocket 20 and take-up reel 21 through a friction clutch 22driven through belt 27. An idler 23 presses the film into engagementwith sprocket 20 thereby pre venting tape slippage. Tension is given tothe idler 23 through pivoted arm 24 which is under tension from spring25 attached-to lever 26.

Electric heater 30 furnishes heat to control the temperature of thecabinet 13 to a constant value and motor 28 drives the squirrel cageblower 29 which circulates air through the drying compartment 13 aboutbaffie 13b.

The heater 30 is shown in Figure 1, but for simplicity has been omittedfrom Figure 2. Radiating fins 31 and 32 are attached to heater 30 to aidin conduction of the heat. The temperature within the drying chamber 13is maintained constant by thermal regulator 33 and the temperature isindicated by thermometer 34.

The treating or impregnating station 35 includes the trough 36 withinconstant temperature bath 37. The trough 36 is provided with parallelknife edges 38 and 38a which act like a ruling pen (see Figure 2a)permitting a 0.375 inch trace of chemicals to be impregnated in thegelatin coating on the tape 39. Excess liquid is removed from thegelatin surface by transverse scraper 40.

The constant temperature bath 37 comprises an aluminum block and thetemperature is maintained constant by strip heaters 41 and 42 which arecontrolled by thermal regulator 43, electrical power being brought tothe heating elements by lead 44. Pilot li ht 45 indicates when thecurrent is on. Power is furnished to motor 28 and heaters 30, 41 and 42through switch 46, the circuit being fused through 47.

Film or tape 39 from the supply reel 43 passes over rollers 49 and 50which maintain tension on sprocket 51. The supply reel 48 is maintainedagainst a felt brake 52 shown in Figures 3 and 6 and the brake 52 isactuated through lever 53 to which is attached bearing 54. At-

tached to shaft 55 which rides in bearing 54 is drum 56 which is heldagainst brake pad 52 by spring 57 which is anchored by pin 58. The filmsupply reel 48 is held onto shaft 55 by clamp 59.

Referring to Figure '5, the lever arm 53 is supported 1 3 by the panel11. Shaft 55a is held in socket 60 which is fastened to panel 11. Abearing surface for shaft 55a is provided by collar 61, the wholeassembly being held onto the shaft 55a by pin 62. t

Sprocket 51 furnishes additional braking action against the tape 39 frompulley 63, Figures 2 and 7, on which rides a small section of roundleather belting 64 with tension applied by spring 65 which is anchoredby pin 66. All of these wheel-like mechanisms are supported to the panel11 by individual bearing members as shown in Figure 2.

Guide rollers 66 and 67 carry the tape 39 parallel to the exposed uppersurface of the impregnation trough 36 and allow the trough 36 to bevertically adjusted so that the gelatin-coatedsurface of, the tape 39moves over the liquid surface in the trough 36.

The impregnating solution is retained in leveling bottle 69 providedwith a tube connection 70 which permits the solution to flow through theplastic tubing 71 into trough 36. The liquid level in trough 36 israised or lowered by positioning bottle 69 along the threaded rod 72 bycollar 73, which supports bottle clamp 74, the selected position beingsecured by nut 75.

The coating station 35, including the trough 36 and the constanttemperature bath 37, is adjusted by plate 76 which is fastened toplatform 77 by knurled nuts 78 and 79. Loosening the knurled nuts 78 and79 permits plate 76 to be positioned with respect to panel 11 throughslots therein.

Lateral movement of station 35, parallel to panel 11, is controlled bythe studs and knurled nuts 80 and 81 which are fastened to the troughassembly or station 35 through slots in plate 76.

The entire trough assembly 35, plate 76 and platform 77 rest on steelball 82 which in turn operates in socket 83 inplatform 77 and lowersocket 84 in sub-platform 85. Stud bolts 86 and knurled nuts 87 securethe platform 77 and the sub-platform 85 together to clamp the steel ball82 therebetween. Adjustments can be made so as to level the troughassembly 35 and to dispose the trough 36 with respect to the panel 11and the path of travel of the tape 39 to obtain the desired contact ofthe gelatin coating with the liquid surface in the trough 36.

Platform 77 and sub-platform 85 are triangular sections, the apex of thetriangular facing the viewer. Depending from sub-platform 85 is athreaded shaft 89 passing through support collar 90 which is rigidlysecured to panel 11. Knurled nuts 91 and 92 on opposite sides of thecollar 90, through which the shaft 89 freely passes, permits the entireassembly of platforms 77 and 85 through assembly 35 to be raised .orlowered and fixed in the desired position.

The unsensitized film is drawn from supply reel 48 through sprocketassembly 49, 50, 51 over roller 67 along knife edges 38 and 38a andunder rollers 68 and 94, the excess solution being removed from thegelatin coating ,by scraper 40.

After the gelatin coating on the tape 39 has been impregnated with thedesired chemicals it passes over positioning roller 66 and enters thedrying chamber 13 through the port 95. Time for drying the coating isobtained by passing the slowly moving film over positioning rollers 96,97, 98, 99 and drive roller 20. Thence, the film 39 is collected ontakeup reel 21, the temperature-controlled air circulated by blower 29having dried the gelatin coating on the film. It will be noted thatafter the tape 39 leaves the scraper 40 the gelatin side of the tape 39does not touch any component of the apparatus or another portion of thetape 39 until it is fully dried and being accumulated on the take-upreel 21.

A cross-section of the drive sprocket 20, idler 23 and lever arm 24 isshown in Figure 4. The idler 23 is pinned to a pair of levers 24 by apin 100, the other end of the levers 24 operating against the hub andshaft 101. Hub 101 is pinned to retainer bar 102 by rod 103,

4 the entire assembly being fastened to collar 104 through the hub andshaft 101 which passes through bearing 105. The force lever 26 isfastened to pin 106 through spring 25 which furnishes the necessarytension.

The described apparatus has been used successfully for the preparationof sensitized tape for use in connection with the hydrogen sulfideanalyzer-recorder described in our co-pending application Serial No.375,032, filed August 18, 1953, now Patent No. 2,800,397 and entitledHydrogen Sulfide Analyzer Recorder.

The tape 39 comprises a uniformly transparent strip having a sensitizedplastic absorptive coating such as of gelatin or agar agar. The strip isof non-reactive, nonporous, non-absorptive fiexible material such ascellulose acetate. A suitable base strip for our hydrogen sulfidesensitive tape is 16 mm. movie film having marginal sprocket-receivingperforations for driving the tape through the sensitizing apparatusdescribed herein and through the hydrogen sulfide analyzer-recorderreferred to above.

The tape is passed along the trough 36 at a rate of about 45 feet perhour and immediately introduced into the drying chamber 13 wherein atemperature of about 113 F. is maintained, the dried film beingaccumulated on reel 21. Under these conditions, a uniform impregnationof the gelatin is obtained, the desired concentration of lead acetatebeing between about 0.25 to 0.30 mg. per sq. cm. which corresponds to 12to 14 mg. per foot of 16 mm. tape.

In preparing such sensitized tape the blank film 39 is fed from supplyreel 48 and the gelatin coating thereof contacted at a temperature ofabout 113 F. in trough 36 with a solution of lead acetate and sodiumacetate.

The solution for sensitizing the plastic coating is 1 normal leadacetate and 1 normal sodium acetate at a pH of about 6.7. The pH isimportant because if too much acidity is present, sensitivity tohydrogen sulfide is decreased whereas if the acidity is too low, thelead will precipitate from the sensitizing solution with the result thatsubstances such as mercaptans will have greater effect on the stainingof the tape. The sensitized coating obtained from the defined solutionstains uniformly, has the desired optical density for a givenconcentration of hydrogen sulfide, and has low susceptibility tovariations in optical density.

The coating is not light-sensitive and retains its transmittancy whenexposed to the light beam and photoelectric cell arrangement used tomonitor the moving tape as described in our co-pending application.

The film may be stored for long periods of time without impairingitssensitivity to hydrogen sulfide. Our tape is uniform with respect to itsbuffered lead acetate content and is light-, air-, and age-stable whenprepared pursuant to our system.

A number of batches of tape produced in accordance with the above wereexamined with respect to the uniformity of the sensitized film coating.In making such examination, the gelatin was stripped from the base tapeand treated with hydrochloric acid to produce an extract containing thedissolved lead acetate. The lead content was then determined by means ofa polarographic apparatus with the results illustrated by the data shownin the following table:

Table I Batch The apparatus described may be used on 16-mm. or

5 35-mm. film when the size of the coating trough 36, the block 37, thepad rollers, the supply and take-up reels, and the tension and drivesprockets are appropriately provided.

This application is a continuation-in-part of our copending applicationsSerial No. 375,032, now issued as U. S. 2,800,397, and Serial No.556,238, filed December 29, 1955, entitled Apparatus for Treating OneSurface of a Strip, issued as U. S. 2,884,333.

Although we have described our invention by reference to a preferredembodiment thereof illustrated in the drawings, it should be understoodthat this is by way of example only. Further, it is contemplated thatmodifications in the apparatus and mode of using the apparatus can bemade without departing from the scope and spirit of the describedinvention.

What we claim is:

1. The method of preparing a gelatin-coated tape which is quantitativelysensitive to hydrogen sulfide and which is light-, air-, and age-stablewhich comprises the steps of sensitizing a gelatin coating supported bya transparent gas-impervious tape with 0.25 to 0.30 mg. lead acetate persq. cm. from an aqueous solution comprising 1 normal lead acetate and 1normal sodium acetate by exposing only the coated surface to a pool ofthe solution, a

and subsequently drying the sensitized gelatin coating.

2. The method for preparing a hydrogen sulfide sensitivefluid-impervious transparent tape, said tape supporting a waterabsorptive coating which contains from 0.25

to 0.30 mg. lead acetate per sq. cm. and is quantitatively sensitive tohydrogen sulfide, the steps which comprise contacting the coating withan aqueous sensitizing solution bymoving said tape over an elongatedbody of the solution with said coating running over the surface of saidbody, said body comprising an aqueous solution of 1 normal lead acetateand 1 normal sodium acetate maintained at a pH of about 6.7, removingexcess solution from the coating as it emerges from said body, and

is specifically responsive to hydrogen sulfide and which is light-,air-, and age-stable which comprises the steps of impregnating agelatin-coated transparent gas-impervious tape with 0.25 to 0.30 mg.lead acetate per sq. cm.

by contacting the gelatin coating directly with an extended surface of apool of a solution comprising 1 normal lead acetate and 1 normal sodiumacetate at pH of about 6.7, and subsequently drying the treated gelatincoating.

5. The process of impregnating a supported gelatin coating with 0.25 to0.30 mg. lead acetate per'sq. cm. deposited from an aqueous solution of1 normal sodium acetate and 1 normal lead acetate at pH about 6.7 whichcomprises maintaining an elongated body of liquid impregnating solution,passing the gelatin coating in contact with the surface of saidsolution, removing excess solution from the gelatin coating at a pointadjacent at end of said body and returning the removed excess to saidbody, and drying the impregnated gelatin coating by passing through adrying zone.

References Cited in the file of this patent UNITED STATES PATENTS OfiuttJuly 23, 1957

1. THE METHOD OF PREPARING A GELATIN-COATED TAPE WHICH IS QUANTITATIVELYSENSITIVE TO HYDROGEN SULFIDE AND WHICH IS LIGHT-, AIR-, AND AGE-STABLEWHICH COMPRISES THE STEPS OF SENSITIZING A GELATIN COATING SUPPORTED BYA TRANSPARENT GAS-IMPERVIOUS TAPE WITH 0.25 TO 0.30 MG. LEAD ACETATE PERSQ. CM. FROM AN AQUEOUS SOLUTION COMPRISING 1 NORMAL LEAD ACETATE AND 1NORMAL SODIUM ACETATE BY EXPOSING ONLY THE COATED SURFACE TO A POOL OFTHE SOLUTION, AND SUBSEQUENTLY DRYING THE SENSITIZED GELATIN COATING.